Oxidative stress contributes importantly to the pathophysiology of many types of cardiovascular disease. Nitroxides are relatively stable free radicals that have been used as redox-sensitive MRI contrast agents in preclinical studies to assess tumor redox status. We implemented a dynamic nitroxide-enhanced MRI method to test the hypothesis that MRI can detect cardiac oxidative stress in vivo. Imaging was performed in untreated controls and mice infused with angiotensin II for 7 days. The MRI signal decay rate in the heart was significantly higher in the angiotensin II group, indicating that these methods detect cardiac oxidative stress due to angiotensin II infusion.